function unique(arr) {
    let set = new Set();
    for (let str of arr) {
        set.add(str);
    }
    let result = [];
    for (let str of set) {
        result.push(str);
    }
    return result;
}

let values = ["Hare", "Krishna", "Hare", "Krishna",
  "Krishna", "Krishna", "Hare", "Hare", ":-O"
]; 

alert(unique(values));